Most conventional automatic transmissions have three forward speed ranges: Low, Second and Drive. The automatic transmission can normally be upshifted and downshifted through these ranges simply by pivoting a shift lever, mounted either on the steering column or center console, incrementally in a single plane. When rapidly shifting gears during racing, the lever must be pivoted carefully to prevent overshifting, or undershifting.
In a vehicle having a conventional three speed manual transmission, upshifting or downshifting through the three forward speed ranges is accomplished by moving the shift handle in the well-known H-shaped shifting pattern. In such pattern, the shift lever is normally advanced in a dog-leg pattern through a gate when shifting between first and second gears, and in a straight line pattern when shifting between second and third, or between first and reverse. Floor mounted H-pattern shifters have been, and continue to be, popular automotive after-market products.
H-pattern shifters for use in changing gears in vehicles are disclosed in U.S. Pat. Nos. 2,097,566 and 2,488,469. Both of these shifters are intended to be used in combination with manual transmissions. In each of these shifters, however, the shift handle is operatively connected to a pair of transmission actuators.
There have been some attempts to provide for an automatic transmission, a shifter which upshifts and downshifts the transmission through its three forward speed ranges in response to movement of a shift handle in a generally H-type pattern. An example of such a shifter may be found in U.S. Pat. No. 3,465,612. Another shifter which permits shifting in either a straight line or a modified H-pattern is disclosed in U.S. Pat. No. 4,326,432. While each of these automatic transmission shifters may function entirely satisfactorily for its intended purpose, there is a need for an H-pattern shifter which prevents inadvertent overshifting or undershifting, which is relatively simple in construction and reliable in operation, and which accomplishes these ends utilizing a relatively long lever with a short throw to afford installation in confined spaces.